1. Field of the Invention
The invention relates to a process for manufacturing a cellulosic yarn by spinning a solution of cellulose in a tertiary amine oxide, the solution possibly containing water and/or a stabilizer, to form fibers or filaments, coagulating, washing, and drying.
2. Discussion of Related Art
W095/24524 discloses a process for improving the color characteristics of woven fabrics made from so-called Lyocell yarns. Lyocell yarns are solvent-spun cellulose yarns manufactured by spinning a solution of cellulose in an organic solvent. The solvent is essentially an aqueous tertiary amine oxide, for example N-methylmorpholine-N-oxide (NMMO). In accordance with W095/24524, woven fabrics made from the cited cellulose yarns are subjected to a mercerizing process, i.e., treated with an alkaline solution. This mercerizing corresponds in principle to that common for cotton woven fabrics, and it is preferred to employ an aqueous NaOH solution with a concentration of 10 to 30% by weight at room temperature or a somewhat higher temperature (for example, up to 35.degree. C.). Subsequently, a washing of the woven fabrics with water can be carried out. To neutralize the lye bath, the fabric is treated with a diluted aqueous acid, washed repeatedly to remove the acid, and then dried. According to the examples in W095/24524, in which aqueous NaOH solutions were employed in concentrations of 14% and 25% by weight, respectively, the treatment of woven fabrics made from Lyocell yarns was carried out at room temperature over a period of 45 seconds. The woven fabrics obtained exhibited a deeper shade after dyeing than non-mercerized fabrics. Although the appearance of the mercerized fabrics was better after 5 washings than that of non-mercerized fabrics, and the yarns of the mercerized fabrics had shorter fibrils than non-mercerized fabrics, it was shown that this mercerizing conducted on the fabrics, i.e. on yarns that had previously been dried, led among other things to a deterioration of the textile properties, especially the strength.